Grinding wheels or groups of grinding wheels may be releaseably secured on a wheel spindle to permit them to be exchanged if, for example, they become worn or if, in respect of different machining operations, they are to be exchanged.
Grinding wheels for spectacle-lens-edging machines may be provided with a cylindrical region and a grooved region. The cylindrical region may be used to pre-machine a spectacle lens to shape and the grooved region may be used to form a bevel on the circumference of the shaped spectacle lens. More than one grinding wheel may be used, for example, three grinding wheels, of which one grinding wheel may be provided for machining plastic lenses, a cylindrical grinding wheel may be provided for the rough grinding of spectacle lenses made of silicate glass and a grinding wheel with a bevel groove may be provided for precision or fine machining and beveling.
The wheel spindle and the grinding wheels are arranged on the spectacle-lens-edging machine in a grinding chamber, which may be closed on all sides to prevent abraded material produced during grinding and a cooling lubricant from passing to the outside. The cooling lubricant may be sprayed into the grinding region between the grinding wheel and the spectacle lens. Although the grinding chamber is kept as small as possible, a spray guard may be arranged tightly around the grinding wheels, said spray guard only leaving the grinding region exposed and having contact shoe regions, on which the unmachined lens and/or the ground-to-shape spectacle lens is positioned to be measured.
The grinding chamber may define a confined space, which may make it very difficult to exchange grinding wheels or groups of grinding wheels, since the grinding wheels are connected to the wheel spindle such that a grinding-wheel-retaining shaft, which is connected integrally to the wheel spindle and has a smaller diameter than the wheel spindle, has a sleeve having a length smaller than the width of the grinding wheel(s). The sleeve bears the grinding wheels and centers them, while a retaining disk braces the wheel spindle, the retaining disk having a greater diameter than the diameter of the sleeve. The retaining disk may be screwed to the grinding-wheel-retaining shaft to brace the grinding wheel with the wheel spindle.
To remove the grinding wheels, the grinding chamber must have enough space sufficient to permit the grinding wheels to be withdrawn from the grinding-wheel-retaining shaft and the grinding chamber, individually or together.
Furthermore, the grinding chamber must have enough space sufficient to permit a suitable wrench to attach to a screw connection of the retaining disk to clamp and release the connection. Finally, a double tolerance is provided between the grinding-wheel-retaining shaft and the sleeve and the sleeve and the grinding wheel or the group of grinding wheels, said double tolerance adversely affecting the concentric-running properties.
If the initially mentioned spray guard with the contact shoes is present, the guard may need to be removed before the grinding wheel(s) is removed.
In the case of prior art spectacle-lens-edging machines, the task of exchanging a grinding wheel or a group of grinding wheels is thus time-intensive and requires a certain amount of skill.